Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 250407

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1207 AM EDT Fri Sep 25 2020


Deep mid to upper level high pressure between 700-400mb will be
centered over Southeast Michigan tonight. Flow trajectories over the
area will remain strongly anticyclonic out of the east, maintaining
a dry air feed directly into Southeast Michigan. Cloud exists north
of the Saginaw Valley, along a modest stretching deformation axis.
Forecast soundings pin subsidence maximum at roughly 6.0 kft agl
tonight, then centering a secondary subsidence max at roughly 16.0
kft during the daylight hours Friday. Fog has developed in the
Saginaw Valley this evening. Low confidence exists with longevity.
VFR to potential MVFR hz will be possible at DTW again at daybreak
Friday morning. Light west wind tonight will trend light south
southwesterly by Friday afternoon.

For DTW...VFR to potential MVFR hz will be possible at daybreak
Friday morning.


*  None.


Issued at 329 PM EDT Thu Sep 24 2020


Warm weather carries into the Weekend, but a big pattern shift to
take place next week.

Once again temperatures making a run toward 80 degrees in spots this
afternoon with the low level southwest flow and plenty of sunshine.
Mid level cold (-15 C at 500 MB) pool/upper wave exiting the
Minneapolis area will track harmlessly to the southeast tonight into
the western Ohio Valley, as pronounced upper level ridge builds into
the Western Great Lakes. This will allow weakening cold front to
wash out over the Central Great Lakes. With the ill defined pressure
pattern, dew pts holding in the 50s, and winds going calm tonight,
patchy fog will be possible but probably highly localized and not
worth a mention in the zones. Low level winds a bit more south-
southeast tomorrow, along with some late day moisture advection
should be enough to keep boundary layer mixing depths to come up
short of the 850 MB level, but still looks like max temps reaching
into the upper 70s/near 80 degrees with 925 MB temps of 18+ C.

Strengthening low level southwest flow Friday night-Saturday ahead
of yet another dissipating cold front should result in even warmer
temperatures for Saturday, with 850 MB temps of 15+ C suggestive of
low to mid 80s, although still going to be a challenge to mix to
that level. Regardless, should become a bit breezy, with gusts to 25
MPH indicated late in the day. There is instability axis (negative
showalter index) to content with as low level jet tracks through
Saturday night, but mid levels look too warm and dry to support

Energetic Pacific energy to track through the Northern Rockies over
the weekend, with additional energy diving out of the Gulf of Alaska
helping to carve out a longwave trough over the Central Conus,
absorbing the remaining upper level energy/wave over eastern Texas in
the process. The operational Euro remains on the stronger envelope
of the solutions when compared to GFS ensemble members for early next
week, but the general theme of large upper level low center
developing over/near the Great Lakes region remains valid for the
mid week period. Increasing FGEN and surface low tracking in between
Central/Eastern Great Lakes should be able to support showers and
possibly an embedded thunderstorm in the Monday-Tuesday time frame
before the deepening low pressure tracks into eastern Canada driving
much colder air into the Great lakes region. 850 MB temps look to
drop below zero by Friday, just under 10 percent moving average
based on SPC climatology page. Max temps stuck in the 50s appears
likely at the end of the forecast period, as moisture flux from Lake
Michigan contributes to mostly cloudy skies.


Disjointed high pressure persists to the south while a cold front
stalls over northern Lake Huron. The bulk of the associated showers
will remain mainly over the open waters of Lake Huron. Winds drift
toward the south with drier weather during the day on Friday. A
stronger cold front arrives on Saturday bringing gusty showers and
perhaps a few thunderstorms, mainly for Lake Huron. Small Craft
Advisories may be needed as gusts near 22 knots during the afternoon
with southwest flow. After the front clears east, a cooling trend
ensues with daily chances for showers with breezy conditions. A
strong low pressure system could trigger marine hazards Monday into
Tuesday with a tight pressure gradient field and an extended period
of heightened waves.


Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.



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